The Quadrangular and Triangular Space of the Shoulder
The axillary and radial nerves branch from the posterior cord of the brachial plexus. They innervate muscles of the posterior shoulder and upper arm, respectively, and give off cutaneous branches as well. The radial nerve continues deep to the intermuscular septum (between the medial head of the triceps and brachialis) to innervate the posterior forearm and hand.
Format: Anatomical plate intended for textbook publication.